DESCRIPTION TITLE OF THE INVENTION CONTACTLESS COMMUNICATION MEDIUM TECHNICAL FIELD [0001] The present invention relates to a contactless communication medium. BACKGROUND ART [0002] Conventionally, a technology of providing an antenna on a substrate and connecting the antenna to an IC module to form a contactless communication medium such as an IC card, an IC tag or the like which can perform data communication with an external read/write device is known. CITATION LIST [PATENT LITERATURE] [0003] [PTL1] Japanese Patent Publication No. 3721520 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION [0004] With the above-described conventional technology, when an inlet including an IC module mounted on an antenna sheet which has an antenna is combined with an insulating substrate or the like and the resultant assembly is used as a contactless communication medium, the substrate is made thick due to the thickness of a mold part or the like containing an IC chip sealed therein. Therefore, the inlet including the IC module mounted on the antenna sheet is combined with an inlay substrate having an opening in positional correspondence with the mold part so that the mold part is exposed from the opening. [0005] In an IC card or the like, the outermost layer of the inlay is held between insulating resin substrates in a laminated manner; thus no serious problem occurs even with the above-described structure. However, especially, in the case where the inlay is in the outermost layer and thus the IC module part is exposed to the outermost layer, as in an electronic passport or the like, or in the case where the inlay is covered merely with a paper material or the like which is weak against electricity, the IC module is likely to be influenced by an external impact or the like. This causes malfunction or communication disorders of the contactless communication medium. [0006] The present invention, made in order to solve the above-described problems, has an object of providing a contactless communication medium for reducing the influence of an external impact or the like on an IC module and thus reducing the possibility of malfunction or communication disorders, even with a structure in which a mold part of the IC module is exposed from an opening provided in a substrate of the inlay. SOLUTION TO THE PROBLEMS [0007] To achieve the above objects, a contactless communication medium according to the present invention comprises a first substrate, a second substrate, an antenna formed on the second substrate, and an IC module connected to the antenna. The IC module has at least a lead frame, an IC chip mounted on the lead frame, and a mold part for sealing the IC chip; the first substrate has an opening for exposing the mold part; the second substrate has a hole or recessed part for accommodating at least the mold part, the hole or recessed part having an area size larger than the mold part; a sealing member having an insulating layer and an adhesive layer in a stacked manner is located so as to cover the mold part, the sealing member being bonded to the mold part via the adhesive layer; and where the sealing member has a transverse width x and a longitudinal width y, the hole or recessed part of the second substrate has a transverse width a and a longitudinal width b, and the first substrate has a thickness of d, at least one of expressions : x < a + 2d... (1) and y A sample was created in substantially the same method as in Example 1 except that the sealing member was not used. [0090] The cross-section of each obtained contactless communication medium was measured with an electronic microscope. Gaps of about 50 um were made between the inner side surfaces of the opening of the first substrate and the IC module, and the step between the outer surface of the mold part of the IC module and the outer surface of the substrate having the opening was larger than 20 um. [0091] The above-described static electricity test was performed. Communication response disorders occurred at some of the voltages and at some of the positions. The result of the above-described ballpoint pen test shows communication response disorders occurred. The result of the above-described stamp test shows communication response disorders occurred. By contrast, the result of the line pressure test shows the mold part was not confirmed to have been cracked even though there was no sealing member. [0092] Based on the above-described results, in this embodiment using the sealing member, the invasion of static electricity into the IC chip can be prevented. By fulfilling the flatness requirements on the outer surface, the occurrence of disorders in the ballpoint pen test or the stamp test can be prevented. In addition, the sealing member is prevented from contacting the second substrate, and thus the mold part can be prevented from being cracked in the line pressure test. By contrast, in Comparative Example 1 in which the sealing member is not used, the probability that the communication response disorders occur after each of the tests other than the line pressure test is very high. DESCRIPTION OF THE REFERENCE CHARACTERS [0093] 1 ... contactless communication medium 2 ... first substrate 3 ... second substrate (antenna sheet) 4 ... IC module; 41 ... IC chip, 42 ... mold part, 43 ... lead frame, 431 ... die pad, 432 ... terminal part, 44 ... bonding wire 5 ... sealing member 61... antenna, 62 ...jumper wire, 63 ... conduction part, 64 ... connection part, 65 ... hole 7... inlay sheet 8... cover sheet 9 ...bookletpart We Claim: [Claim 1] A contactless communication medium, comprising: a first substrate, a second substrate, an antenna formed on the second substrate, and an IC module connected to the antenna; wherein: the IC module has at least a lead frame, an IC chip mounted on the lead frame, and a mold part for sealing the IC chip; the first substrate has an opening for exposing the mold part; the second substrate has a hole or recessed part for accommodating at least the mold part, the hole or recessed part having an area size larger than the mold part; a sealing member having an insulating layer and an adhesive layer in a stacked manner is located so as to cover the mold part, the sealing member being bonded to the mold part via the adhesive layer; and where the sealing member has a transverse width x and a longitudinal width y, the hole or recessed part of the second substrate has a transverse width a and a longitudinal width b, and the first substrate has a thickness of d, at least one of the following expressions: x